Electric safety lamp



Dec. 26, 1950 w, STAMPER 2,535,819

ELECTRIC SAFETY LAMP Filed Dec. 13 1945 I I Mi -lg! INVENTOR. Willsorz. Stamper BY r? Arman/5y Patented Dec. 26, 1950 UN 1 TED STATES PATENT OFFICE ELECTRIC SAFETY LAMP Willson Y."Stamper, Newark, N. 3., iassig'nor to Thomas A. Edison, Incorporated, West Orange, N. -J., a corporation of New Jersey Application'December 13, 1945,"Serial No.634,824

3 Claims. 1

This invention relates to electric lamps which are especially adapted for use in mines or other places where explosive gases are likely to be present, but it will be understood that the invention is not necessarily limited to this particular use.

It is an object of my invention to provide an improved form of such a lamp which is highly safe and dependable for the purposes above stated and which has a very simple and economical construction.

It is particularly an object to provide a novel and improved construction of electric safety lamp which is adapted to prevent workmen or unauthorized persons from tampering with the lamp, or gaining access to any part thereof, such as might cause damage to the lamp or accidentally produce a spark that could set off an explosion were highly combustible gases present in the surrounding atmosphere.

It is another object to provide improved exteriorly accessible devices for adjusting safety lamps, and particularly for locking the bezel thereof, which are safeguarded against being tampered with by unauthorized persons.

It is another object to provide a novel-means for focusing safety lamps without n'eedfor gaining access to the interior of the lamp.

It is another object to provide an improved mechanism for instantly breaking the circuit and/or quenching the filament of safety lamps upon the glass envelope of the lamp being ifractured or broken.

Other and allied objects and features of my invention will more fully appear from the following description and the appended claims.

Figure 1 is a view of an electric safety lamp according to my invention showing parts thereof in section substantially on the line |-I of Figure 2';

Figure 2 is a sectional viewtaken substantially on the line 2-2 of Figure 1;

Figure 3 is a fractional View similar to Figure l but showing the circuit breaker for the lamp in open position; I

Figure '4 is a fractional sectional view taken substantially on the line 4-4 of Figure 3.;

Figure 5 is a fractional sectional view taken substantially on the line 5-'5 of Figure 3;

Figure 6 is a fractionalsectional view taken substantially on the line 6--'6 of Figure 3; and

Figure "I is a fractional sectional view taken on the line 'l-J of Figure 5.

The present lamp has a casing HI, molded for example oirplastic, which is generally semispher- "ical in shape but provided with a wide rib l ne running across the to and back sides "thereof. Firmly secured to the back part of the casing, as by screws not shown, is a clip 0b for attaching the lamp to amineflsc'ap or the like. Mounted in the front portion of "the casing is a parabolic reflector 'l-l. This reflector has a peri heral flange Ha seated in an annular recess l2 rovided in the 'frontedge of' the casing. Across the front of the reflector is ale'ns "l3 wh-ich is clamped tightly against the flange Ha by abezel N that is threaded exteriorly onto the casing. For sealing purposes, there maybe interposed a resilient gasket ring it between the lens and the reflector as shown.

Within the casing near the hack -wall thereof there' -is a channeled metal .ifalne I 6 'ofa U shape as viewed from the side,th-is frameh'aving two legs 16a and [Eb which extend towards the front of the casing adjacent diametricallyopposite wall portions thereof. The frame carries a switch lever I! which bridges substantially the space between the two legs thereof. "This switch lever comprises two similarmetal parts 1111 land Hb. These parts have studs I8 Welded thereto "which lpivotally engage insulating bushings 18a in the side flanges of the leg 16a of the frame. These metal parts have arcuate central portions spotwelded to a socket 19 for an electric light bulb 20, this socket having two slots Illa in the walls thereof which are offset at their inner ends for receivingthe pins on the base portionof the bulb and locking the bulb in Zplace in the usual rash-- ion. Beyondthe socket 19 with respect to the pivots l-B the parts Ila join to form a single switch blade llc. This switch blade terminates between two stops -2Ia and 21b which define the range of angular movement of the switch lever ll. The stops are integral portions of fan insulating member 21 made iorexa'mple of suitable plastic, which is secured by a :screw "22 to the leg 16b of the frame. Mounted on the outer one of the stops Zia, and held thereto by a screw 23, is a "switch member having two spring contactarms 24 that straddle the switch blade We and "span the range of :movement thereof. The switch blade is thus out of contact with these contact arms when it is in an outer or "open position. The contact arms however converge at a place adjacent to the inner stop 21b so "that the switch blade will engage therewith when itis inaninner or closed position. As is hereinafter explained this switch is provided for instantly breaking the circuit of the lamp upon the :glass envelope of the light bulb 20 being fractured or broken,

The light bulb may typically have two filaments and 26 and therefore two respective end terminals on the base portion thereof only one of which is shown as 27. It will be understood that the metal shell of the base portion of the bulb constitutes a third or common terminal for the filaments. Electrical connections to the end terminals of the bulb are made by two respective spring arms 28 and 29 which are supported insulatedly in a stack 30 held to the frame 56 by a screw 3|. These springs project beyond the stack 30 in directions outwardly with respect to the casing and bear slidably against the spindle of a rotary hand switch generally referred to as 32.

This spindle comprises a metal cylinder 33 having two transverse slots 34% and 35. These slots are oriented 180 from each other about the axis of the cylinder and have depths equal to a major fraction of the diameter of the cylinder. Mounted in these slots are respective insulating members 36 and 31 which have the shape of segments of a cylinder. The insulating members are locked in the slots by a shaft 38a which extends therethrough and axially through a part of the length of the cylinder 33; this shaft has an end portion of enlarged diameter which projects beyond the inner end of the spindle and engages a slot id in the casin as shown in Figure 2. Extending axially through the outer end portion of the spindle is a shaft 38 held thereto by a set screw as shown. This shaft 38 is journalled in a bearing 39 which is an integral part of the casing. in assembling the lamp, the spindle with the shaft 38a is first installed in the casing and then the shaft 38 is passed through the bearin and secured in the spindle. In order that the spindle may be readily turned by hand there is a knurled plastic knob M provided on the exterior end of the shaft 38.

Electrical connection to the metal cylinder of the switch is made by a spring arm 32 secured at 43 onto an interior ledge of the casing. The part of this spring which engages the cylinder is slightly ridged (see Figure l) and the portion of the cylinder engaged by the spring has four equally-spaced peripheral notches (it so that the spring will detent the spindle of the switch at 90 intervals. The portions of the cylinder 33 which complete the circumference of the spindle at the insulating members 36 and M subtend approximately 90 angles about the axis of the spindle and are oriented 180 from each other in view of the corresponding orientation of the slots 3 and abovementioned. When the spindle is detented in the angular positions shown in Figure l and 2, the springs 28 and 29 engage the insulating members 36 and 3? to place the switch 32 in open condition. As the spindle is turned 95 from this position one or the other of the springs 28 or 29, depending upon the direction of turning of the spindle, will contact the cylinder 33 and close the circuit of the filament 25 or 26; upon turning the spindle another 90 interval in the same direction both springs will again engage the insulating members 36 and ti to place the switch again in open condition; and upon further turn ing the spindle through a 90 interval in the same direction the other of the springs 28 and 29 will engag the metal cylinder 33 and close the circuit to the other filament of the light bulb, it being understood that the next succeeding position of the switch is again one wherein the circuits of both filaments are open.

Electrical current is supplied to the lamp by way of a two-conductor cable 45 which passes 4 through the metal clip [0b and an aperture 46 in the ribbed portion of the back wall of the casing. This cable is sealed to the casin by a rubber bushing ll in the aperture 46, and is anchored to the casing by the abutment of a metal clamp 35a on the cable against the clip lBb.

To prevent the cable from being bent sharply where it leaves the casing there is a ferrule 41a around the cable, which is staked to the clip and provided with a flared exterior portion. One lead wire 13 of the cable connects to the spring 42 and the other lead wire 49 to the switch contact members 24. The completed circuit through the lamp is therefore by way of lead wire 48, spring arm 52, cylinder 33 of the switch 32, spring arms 28 or 29 and the correspondin end terminal of the light bulb, the filament 25 or 26, the shell of the socket l9, switch blade ill), and switch contact arms 25 to the other lead wire 59.

The switch lever H is urged into open position by the pressure of the two arms 28 and 29 against the end terminals of the light bulb. This switch lever is however normally held in closed position by an arm 5a which engages the envelope of the bulb near the outer end thereof as shown in Figure 1. This arm is carried by a spring 5| that is mounted in the stack 30, and extends through a slot 52 in the reflector H. The spring 5i is strongly biased so as to press the arm 59 against the glass envelope of the bulb with a strong force sufilcient to overcome that of the spring arms 28 and 29. If the glass envelope of the bulb is cracked, it can no longer withstand the force of the arm 50. Therefore the arm serves to crush the glass envelope immediately following the instant the bulb is fractured. In so doing, the arm comes to bear against the spindle of the switch 32 as shown in Figure 3. The springs 28 and 29 are therefore no longer opposed by the arm 5% and immediately swing the switch lever ll into open position to break the circuit of the lamp and prevent any possible explosion of surrounding gases by the filament of the light bulb.

Preferably the arm 59 is mounted so that its path of movement extends through the filaments 25 and 26 of the light bulb. When the envelope is fractured the arm therefore moves through the filaments and destroys them.

In order to focus the present lamp the light bulb 26 is mounted so that it can be carefully adjusted relative to the reflector ll. Typically, the light bulb need be adjustable only in a, direction along the axis of the reflector and a transverse direction at right angles to the filaments since in directions along the filaments the positioning of the bulb with respect to the reflector is not critical. Accordingly, I position the slots 19a in the socket It so as to locate the light bulb with the filaments thereof transverse to the frame i5 (see Figure 2) and mount the frame in the casing so that it is adjustable along the axis of the reflector and in a transverse direction at right angles to the filament. This mounting for the frame comprises a pair of compression springs 54 which are set in interior holes provided in the back wall of the casing and which bear against the frame to urge it along the axis of the reflector. These springs are held constrained, and the frame it is secured to the back wall of the casing, by a screw 53 at the axis of the reflector. Secured to the leg lBb of the frame by the screw 22 is a leaf spring 5i which bears against the side wall of the casing and urges the frame in a transverse direction at right'angles to the filaments 25 and 2B. Thisspring is held constrained, and secured to the casing, by a screw 58 which passes through the spring and threads into a nut 59 at the inner side of the spring. The spring however has a slot 60 through which the screw passes that allows freedom of adjustment of the frame along the axis of the reflector. It will be understood that by adjusting the screw 56 the bulb 20 can be shifted along the axis of the reflector and that by adjusting the screw 58 the bulb can be shifted in directions at right angles to its filament with respect to the reflector. The heads of the screws 56 and 58 are inset in the casing but accessible from the outside so that these focusing adjustments can be made without having to gain access to the interior of the casing.

A look is provided for the bezel [4 so as to prevent unauthorized workmen from opening the casing and tampering with the lamp mechanism. This lock comprises a flat latch member 61 that is mounted in an exterior groove 62 in the casing running at right angles to the bezel. The latch member has an inturned lug 63 at its far end (with respect to the bezel) which engages a hole 64 in the casing to locate the latch member lengthwise of the groove in a position wherein the nearer or free end thereof lies within a rim portion 65 of the bezel. This rim 65 has a series of interior indentations 65a and intervening catches 65b on its rim as shown in Figure 2. A pin 66 is secured in the side walls of the groove and overlies the latch member near its far end so as to lock the latch member to the casing and hold it in the groove. The latch member is movably held in place so that the free end portion thereof can be urged inwardly against the bottom of the groove to free it from the catches 65b and allow the bezel 14 to be threaded onto and removed from the casing. Below the latch member near the rim 65, however, there is a screw 61 threaded into a metal insert 68 in the casing. At the head of this screw there is a small opening 69 in the spring to provide access to the screw for an appropriate adjusting tool. The head of the screw is specially shaped-preferably recessedso that a special tool is required to adjust it.

Preferably I use a screw having a recessed head requiring a small tool non-circular in cross section to adjust it since this permits the hole 69 to be very small and to conceal from the eye the shape of the tool required to adjust the screw. By means of this screw 61 the latch member is forced outwardly after the bezel is threaded onto the casing so that the latch member engages one of the indentations 65a in the rim of the bezel and locks the bezel positively in place.

The embodiment hereinabove described will be understood to be illustrative and not limitative of my invention since the same is subject to changes and modifications without departure from the scope thereof, which I endeavor to express according to the following claims:

I claim:

1. In an electric safety lamp including an electric light bulb: the combination of a frame; a mounting in which said electric light bulb is held, said mounting being pivoted to said frame; a contact spring mounted on said frame for engaging an end terminal of said bulb; a switch in the circuit of said lamp including cooperable contacts of which one is carried with said mounting; and means for engaging the glass envelope of said bulb and pressing the bulb yieldably against said contact spring so as to hold the contact spring flexed and said switch closed, said contact spring pivotally moving said mounting to open said switch upon a release of said engaging means from said bulb caused by a breakage of the envelope of the bulb.

2. In an electric safety lamp including a frame and an electric light bulb: the combination of a movable mounting on said frame in which said electric light bulb is held; a contact spring for engaging an end terminal of said bulb under pressure; a movable member urged against the glass envelope of said bulb and overpowering said contact spring to retain said mounting normally in a predetermined position; and a switch in the circuit of said lamp including a stationary contact carried with said frame and a cooperating movable contact carried with said mounting, said switch being held closed when said mounting is in said predetermined position, and said mounting being moved by said contact spring upon said envelope being broken to cause a release of the pressure of said movable member against the bulb whereby to open said switch and extinguish the filament of the bulb.

3. In an electric safety lamp including an electric light bulb: the combination of a frame; a switch for said lamp comprising a switch memberpivoted insulatedly to said frame and a switch contact mounted on said frame with which said switch member is movable into and out of engagement to place said switch into closed and open positions; a socket in which said light bulb is mounted, said socket being carried with said switch member; a contact spring mounted on said frame and engaging an end terminal of said bulb to urge said switch into open position; and spring-actuated means mounted on said frame and engaging the glass envelope of said bulb to urge said switch into closed position, said spring-actuated means being adapted to exert force upon said bulb, upon said envelope being unbroken, which overpowers said contact spring and normally holds the switch in closed position.

WILLSON Y. STAMPER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,186,454 Toler June 6, 1916 1,345,212 Monahan June .29, 1920 1,453,281 Persons May 1, 1923 1,514,637 Teipel Nov. 11, 1924 1,586,795 Godley June 1, 1926 1,806,868 Wolf May 26, 1931 1,965,664 Millspaugh July 10, 1934 2,204,752 Desimone June 18, 1940 2,250,644 Meginniss July 29, 1941 2,312,613 Wheat Mar. 2, 1943 

